Push delimiter as x_delim_char for Authorize CIM Gateway

While you can specify a `delimiter` when initializing a `AuthorizeNetCimGateway`, ActiveMerchant doesn't send this information to Authorize (it relies on you changing it globally using the web admin). Since `delimiter` is used to parse each response, we should also send it with each request. The CIM gateway allows this by sending `x_delim_char` via `extraOptions`.

`extraOptions` should also be submitted as CDATA instead of plain tag content - this only became a visible problem when appending multiple parameters. You can see an example on page 33 of https://www.authorize.net/support/CIM_XML_guide.pdf